Endo-1,4-α-D-glucan glucohydrolase (α-amylase, EC 3.2.1.1) is currently used in a broad array of industrial applications. These applications include starch hydrolysis for the production of ethanol and high fructose corn syrup, starch soil removal in laundry washing powders and dish-washing detergents, textile de-sizing, the production of modified starches, baking, hydrolysis of oil-field drilling fluids, and paper recycling.
Corn is milled to obtain cornstarch and other corn-milling co-products such as corn gluten feed, corn gluten meal, and corn oil. The starch obtained from the process is often further processed into other products such as derivatized starches and sugars, or fermented to make a variety of products including alcohols or lactic acid. Processing of cornstarch often involves the use of enzymes, in particular, enzymes that hydrolyze and convert starch into fermentable sugars or fructose (e.g., α-amylase).
To produce ethanol, starch containing fractions derived from wet milling or ground grain from dry grinding are further hydrolyzed into fermentable sugars which are then fermented to make ethanol. Several plant starch processing methods exist including a raw starch process, which involves little to no heating of the milled plant material being processed; or higher temperature hydrolysis of starch frequently referred to as “liquefaction”. In either of these methods for breaking down starch derived from plants, the conventional process involves the addition of alpha-amylase to the milled plant starch in a slurry tank.
Recently a group of α-amylase genes from nature were identified (Richardson et al. (2002) J. Biol. Chem. 277 (29):26501-26507) and subsequent laboratory evolution of these enzymes identified novel and improved α-amylase enzymes with performance characteristics ideal for the corn dry milling process. Additionally, transgenic plants have been developed in which a α-amylase enzyme is introduced into the plants. These plants perform well in fermentation without the addition of exogenous α-amylase, require much less time for liquefaction, and result in more complete solubilization of starch (U.S. Pat. No. 7,102,057).